Plumb filter quality into SkShader::appendStages().

We of course need this to know whether or not to bilerp.

TBR=herb@google.com

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4932

Change-Id: I5fe6d93c1d36d0d53f566f722960fcafb0d8bc3c
Reviewed-on: https://skia-review.googlesource.com/4932
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
5 files changed